This invention relates to gauges and, more particularly, to multi-purpose gauges.
It is well established that a radius of curvature of a given arcuate surface can be established if three points on the arcuate surface are known. Based upon this principle, a number of devices have been suggested. One such device is suggested by Price in U.S. Pat. No. 2,855,687. Price provides a rigid, U-shaped member, the ends of which are rectangularly shaped. A micrometer is inserted through the center of the "U" and extends parallel to the legs of the "U". The micrometer adjustment positions to probe. With the spatial relationship of the U-legs being fixed, the probe completes the parameters for determining the radius of curvature. The inner points of the rectangular ends of the "U" are employed to determine the radius of curvature of convex arcuate surfaces, while the points at the exterior of the U-legs are used to determine the radius of curvature of concave surfaces. Additionally, the micrometer may be used as a depth or height measurement with reference to the feet of the "U".
One disadvantage of the Price device is that the legs are not adjustable. Thus, its application to different and varying arcuate surfaces is severely limited. In addition, the device proposed by Price relies upon the principle that the surface contact will be rigid and unyielding compared to the measuring device itself. Should this not be the case, the device by Price could easily provide a false reading. Furthermore, the Price device is not adaptable to measure and determine the dimensions of various elliptical-shaped objects, nor are its feet suitable for measuring spheres of dimensions which are smaller than the legs.
Still another device for determining the three points on an arcuate surface has been proposed by Harris in U.S. Pat. No. 3,439,430. Harris' device is intended for cylindrical objects only. Curiously, Harris' device can vary the position of the outer measuring legs of the gauge (whereas in Price, these legs are fixed), but the central probe cannot determine the third point of curvature. Instead, it is recited and shown as indicating "deviation". "Deviation" is not defined nor is it indicated how the device can be used to calculate the radius of curvature. Accordingly, while Harris' patent discloses the mathematical formula employed by Price and other devices, the device proposed by Harris fails to show a means for determining the crucial third element: the distance of the central probe above the two outer measuring probes. Further, no means are provided within the device by Harris to actually provide a direct indication of the distance between these probes. In the device by Price, this is known because the outer measuring probes are fixed with respect to one another. Furthermore, because the center probe is not adjustable, the device proposed by Harris cannot be used as a depth or height gauge. The outer probes of the Harris device are like Price--rectangularly-shaped members--and, therefore, ill equipped to measure the dimensions of small objects.
All of the prior art devices are believed to have in common a limited number of measurements. Some devices require the two outer probes to be tangent to the arcuate surface. All appear unsuited to make width measurements, as well as depth, height, and radius measurements.